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  1. JDK
  2. JDK-5094318

REGRESSION: Array cloning is not backwards compatible

    Details

    • Subcomponent:
    • Resolved In Build:
      01
    • CPU:
      x86
    • OS:
      windows_xp

      Description



      Name: jl125535 Date: 08/30/2004


      FULL PRODUCT VERSION :
      java version "1.5.0-beta3"
      Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0-beta3-b60)
      Java HotSpot(TM) Client VM (build 1.5.0-beta3-b60, mixed mode, sharing)

      java version "1.4.2_01"
      Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2_01-b06)
      Java HotSpot(TM) Client VM (build 1.4.2_01-b06, mixed mode)

      A DESCRIPTION OF THE PROBLEM :
      Javac 1.5 has changed array cloning due to Bug ID 4900415. Primarily this change affects method/ctor resolution and may result in a change of behaviour of a program if migrating from J2SE 1.4 to J2SE 1.5 (sample code provided).

      The latest public doc says that the new method resolution algorithm consists of 2 passes (one for backwards compatiblity and the other for varargs/boxing). When taking the first pass the javac should see that array#clone yields "java.lang.Object" not its "real" type.

      STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
      Compile & Execute the sample code using J2SE 1.4 and J2SE 1.5 SDKs.

      EXPECTED VERSUS ACTUAL BEHAVIOR :
      EXPECTED -
      I'd expect to see the message "you gave me an object" in both cases.
      ACTUAL -
      J2SE 1.4 emits the message "you gave me an object".
      J2SE 1.5 emits the message "you gave me an array of ints" (even with the flags "-source 1.4" and "-target 1.4" set at compile time).

      REPRODUCIBILITY :
      This bug can be reproduced always.

      ---------- BEGIN SOURCE ----------
      public class Bug {

      public static void main(String[] args){
      method(new int[0].clone());
      }

      // Java 1.5.0+
      public static void method(int[] array){
      System.out.println("You gave me an array of ints");
      }

      // Java 1.4.2 and before
      public static void method(Object obj){
      System.out.println("You gave me an object");
      }
      }
      ---------- END SOURCE ----------

      CUSTOMER SUBMITTED WORKAROUND :
      Explicit cast will do the job: method((Object)new int[0].clone())

      Release Regression From : 1.4.2
      The above release value was the last known release where this
      bug was known to work. Since then there has been a regression.

      (Incident Review ID: 301333)
      ======================================================================

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            • Assignee:
              ahe Peter Ahe
              Reporter:
              jleesunw Jon Lee (Inactive)
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